The human macula comprises a small cone-dominated fovea surrounded by a parafovea area. The function of the rod and cone photoreceptors is impacted by the physiology of the macula, which can be impacted by many disease states and conditions which interrupt normal macular physiology. By determining the function of the cone photoreceptor pathway, the function and physiology of the eye can be monitored. When the cone photoreceptor pathway functions normally, this suggests that no disease state and condition is present (or if present, are at a very early stage) which effect the macula, fovea, parafovea or the neurological pathways transmitting information from these regions to visual processing centers in the brain. Conversely, when the function of the cone photoreceptor pathway is abnormal, this suggests a disease state or condition is present which impact the macula, fovea, parafovea or the neurological pathways transmitting information from these regions to visual processing centers in the brain, which is manifesting itself as an alteration in cone photoreceptor function. The prior art has taught methods for determining if a subject is suffering from impaired cone photoreceptor pathway function. However, many such methods are cumbersome and time consuming to administer and many lack the specificity and sensitivity of the methods of the present disclosure.
The art is lacking is a method to determine impaired cone photoreceptor pathway function, which produces high test-retest reliability and reproducibility, which can be administered in the clinical setting with decreased burden on the subject and the healthcare provider, and which is simple to administer. The present disclosure provides an apparatus and method for determining cone photoreceptor pathway function by analyzing the responses of the cone photoreceptors as a means to determine if a subject is suffering from or at risk for a disease state or condition which effects the macula, fovea, parafovea or the neurological pathways transmitting information from these regions to visual processing centers in the brain. An exemplary device for carrying out this analysis is also described. The subjects identified with impaired cone photoreceptor pathway function can then be evaluated such disease states or conditions. The disease states include, but are not limited to, age-related macular degeneration, glaucoma, and diabetic retinopathy, among others, as well as other disease state or condition that impact the macula and/or the central vision of the eye. In one embodiment, the disease state or condition is glaucoma. In a specific embodiment, the glaucoma is primary open angle glaucoma (POAG). For example, patients with impaired cone photoreceptor pathway function can be monitored for increased risk of a disease state, such as, but not limited to, glaucoma. In addition, patients identified with such disease states can be monitored to track disease progression and the like. Furthermore, such individuals may be started on early intervention strategies to prevent or delay the progression or onset of the disease state and the effectiveness of such intervention strategies can be monitored.